Video reception systems have been available in various forms for many years. However, the available systems generally include stationary, rigid screens on which the video picture is projected. As used herein, "video" includes cinema, slide projection, television, laser or any other means of transforming a visual image to a light pattern for remote projection toward a viewing surface.
Further, conventional projection screens are flat. A typical projector lens forms a distorted image on a flat screen since a projected pattern is normally spherical in shape. In order to minimize distortion, the camera lens and the projector lenses may be designed to operate together to produce a planar pattern at preselected projection parameters.
The distance from the projector lens to the surface of the screen is relative to the desired image size on the reception surface at a given angle of divergence for light rays emerging from the projector lens. The angle of divergence is inversely proportional to the focal length of the projector lenses. The shorter the distance from the projector lenses to the screen for a given size of the image to be displayed on the screen, the shorter the required focal length for the projector and the greater the spherical aberration and lens distortion for a flat projection surface.
In order to produce a large image on a flat screen with a relatively small distortion, a projector lens having a long focal length must be selected and placed at a distance from the screen sufficient to maintain the spherical aberration (distortion produced by projecting a spherical wave front onto a planar surface) within acceptable limits.
If a compact system is desired, the projection screen must be provided with a concave surface to be compatible with relatively short focal lengths. A concave screen tends to equalize the projection paths from various portions of the lens surface to minimize aberration. It will be appreciated that the greater the screen concavity, the smaller the included angle within which the screen can be viewed by an observer within the concavity.
It is apparent that present video reception systems have substantial distortions unless significant alterations are made to the projection lenses and projection screen. Such alterations have the effect of confining the adaptability and usefulness of any one system to a single coordinated application and assembly.
Yet other problems arise when attempting to project video images for 360.degree., or full circle, presentation. Flat screens leave substantial sector areas about adjoining screens where the picture is not visible. Conventional projection systems are unable to project onto convex surfaces which join to provide a circular surface. In addition, conventional video reception screens with arcuate surfaces are simply not portable.
These and other problems of the prior art are overcome by the present invention which provides an arcuate concave image reception surface and convex image viewing surfaces by projecting internally onto an inflated surface.